New aroma chemicals and nature-identical synthetics which can be produced in an economical and straightforward manner are in demand by the fragrance industry. Such chemicals can be utilized in the duplication of fragrance notes associated with often costly natural materials, and for the creation of new fragrance effects.
The ability to introduce oxygen functionality at the terminal position of the isopropylidene group in terpenes with both regio- and stereochemical control provides access to a wide range of oxygenated terpenes of potential organoleptic value. Such chemicals may actually be present in essential oils or other natural products, or may already be known but not naturally occurring, or may be new. Present technology permits the preparation of some of these oxygenated terpene derivatives using reagents, such as selenium dioxide (see M. Fieser and L. Fieser, "Reagents for Organic Synthesis", Vol. 4, p. 423, Wiley-Interscience, 1974; and E. N. Trachtenberg "Oxidation Techniques and Applications in Organic Synthesis"; R. L. Augustine, Ed., Marcel Dekker, New York, N.Y., 1969, p. 119). However, the formation of malodorous organoselenium by-products can render these products organoleptically unacceptable for fragrance use.
Terpenes containing oxygen functionality at the terminal position of the isopropylidene group have been identified in nature. For example, (E)-2,6-dimethyl-2,7-octadien-1,6-diol having the structure: ##STR2## has been isolated from Greek tobacco by Behr et al., (see Acta Chem. Scand., 1978, B32, 228).
Also, (Z)-2-methyl-6-methylene-2,7-octadienol having the structure: ##STR3## has been found by Granger et al., in the essential oil of certain species of Thymus vulgaris L. (see Phytochem., 1972, 11, 2301). The prior art gives no indication of the organoleptic properties of the above-mentioned chemicals and no prediction of the advantageous organoleptic properties of the novel compounds of this invention can be made.
Furthermore, East Indian sandalwood oil, a valuable essential oil, used in large quantities by the fragrance industry, contains the sesquiterpene alcohols, .alpha.-santalol having the structure: ##STR4## and .beta.-santalol having the structure: ##STR5## both of which are oxygenated at the terminal allylic position.
The santalols are generally considered to account for the main odor of East Indian sandalwood oil. Chemists have long sought syntheses of these compounds (see G. Bauchbauer, Chem. Ztg., 1977, 100, 225 and C. H. Heathcock in J. ApSimon "The Total Synthesis of Natural Products", Vol. 2 Wiley-Interscience, New York, 1973, pp. 481-491).
A major obstacle in the synthesis of .alpha.- and .beta.-santalol is the stereoselective introduction of the Z-allylic alcohol functionality. Previous methods used to prepare the santalols have employed conditions or reagents that are difficult to adapt to an industrial scale, for example, air or moisture-sensitive reagents or low reaction temperatures were required (see, for example, E. J. Corey and H. Yamamoto, J. Amer. Chem. Soc., 1970, 92, 226), or such methods lead to predominantly the less desirable E-allylic alcohols as disclosed in U.S. Pat. No. 3,662,008. Also, U.S. Pat. Nos. 4,272,412 and 4,308,401 disclose a method for preparing halogen containing ionone derivatives by reacting a cyclohexanone derivative having the structure: ##STR6## wherein the dashed line may be either a carbon-carbon single or double bond and R.sub.1, R.sub.2 and R.sub.3 are each the same or different and each represent hydrogen or methyl, are reacted with a hypohalous acid to produce a chemical having the structure: ##STR7## wherein X is a halogen. These chemicals were found to be useful as fragrance materials.